Integral over-running load control valve on tractor remote valve section for agricultural loader boom circuit

Abstract

These and other features and objects are achieved by providing an over-running load control valve integral with the remote valve section of an agricultural tractor to allow it to efficiently work in a multipurpose agricultural environment. A counterbalance cartridge valve, with reverse flow check, is manifolded to an agricultural remote valve section.

Having thus described the invention, what is claimed is:  
     
         1 . In an agricultural tractor having a source of pressurized hydraulic fluid, a manually activated control valve in fluid-flow communication with the source of pressurized hydraulic fluid, and a hydraulically controlled loader boom lift circuit, including at least one hydraulic cylinder with a raise port, a lower port, and a ram therebetween, said raise and lower ports in fluid-flow communication with the control valve, the improvement comprising: 
 said control valve has at least one neutral position, one raise position causing pressurized fluid to flow to said raise port of said at least one hydraulic cylinder to extend said ram, and one lower position causing pressurized fluid to flow to said lower port of said at least one hydraulic cylinder to retract said ram; and    a counterbalance relief valve with a relief pressure setting higher than the lift capacity of said at lest one hydraulic cylinder, said relief valve positioned between said control valve and said raise port when said control valve is in said neutral position, thereby providing a positive, zero leak, lock of said at least one hydraulic cylinder.    
     
     
         2 . The improvement of  claim 1 , wherein: 
 said control valve causing pressurized fluid flow to said lower port in said at least one hydraulic cylinder when in said lower position;    said relief valve has a relief spring to establish the pressure required to operate said relief valve; and    said control valve, when in said lower position, is piloted internally to said relief valve, causing pressurized fluid to act against said relief spring in a set ratio, to reduce the relief setting, thereby causing said ram to retract.    
     
     
         3 . The improvement of  claim 2 , wherein: 
 said at least one hydraulic cylinder is connected to a loader that is raised when said control valve is in said raise position and to lowered toward the ground when in said lower position;    said control valve having at least one float position causing said loader to float on the ground;    a reservoir tank on said tractor in fluid-flow communication with said control valve;    said control valve, when in said float position, causes said raise and lower ports to be in fluid-flow communication with said tank, and said control valve is piloted to said relief valve in said set ratio to counterbalance the relief setting of said spring, whereby free fluid flow occurs from said at least one cylinder to said tank.    
     
     
         4 . The improvement of  claim 3 , wherein: 
 said set ratio is approximately 10:1.    
     
     
         5 . The improvement of  claim 4 , wherein: 
 said at least one hydraulic cylinder is two hydraulic cylinders.    
     
     
         6 . An agricultural tractor loader boom circuit comprising: 
 a source of pressurized hydraulic fluid;    a manually activated control valve in fluid-flow communication with the source of pressurized hydraulic fluid;    a hydraulically controlled loader boom lift circuit, including at least one hydraulic cylinder with a raise port, a lower port, and a ram therebetween, said raise and lower ports in fluid-flow communication with the control valve;    said control valve having at least one neutral position, one raise position causing pressurized fluid to flow to said raise port of said at least one hydraulic cylinder to extend said ram, and one lower position causing pressurized fluid to flow to said lower port of said at least one hydraulic cylinder to retract said ram; and    a counterbalance relief valve with a relief pressure setting higher than the lift capacity of said at lest one hydraulic cylinder, said relief valve positioned between said control valve and said raise port when said control valve is in said neutral position, thereby providing a positive, zero leak, lock of said at least one hydraulic cylinder.    
     
     
         7 . The boom circuit of  claim 6 , wherein 
 said control valve causing pressurized fluid flow to said lower port in said at least one hydraulic cylinder when in said lower position;    said relief valve has a relief spring to establish the pressure required to operate said relief valve; and    said control valve, when in said lower position, is piloted internally to said relief valve, causing pressurized fluid to act against said relief spring in a set ratio, to reduce the relief setting, thereby causing said ram to retract.    
     
     
         8 . The boom circuit of  claim 7 , wherein: 
 said at least one hydraulic cylinder is connected to a loader that is raised when said control valve is in said raise position and to lower toward the ground when in said lower position;    said control valve having at least one float position causing said loader to float on the ground;    a reservoir tank on said tractor in fluid-flow communication with said control valve;    said control valve, when in said float position, causes said raise and lower ports to be in fluid-flow communication with said tank, and said control valve is piloted to said relief valve in said set ratio to counterbalance the relief setting of said spring, whereby free fluid flow occurs from the at least one cylinder to said tank.    
     
     
         9 . The improvement of  claim 8 , wherein: 
 said set ratio is approximately 10:1.    
     
     
         10 . The improvement of  claim 9 , wherein: 
 said at least one hydraulic cylinder is two hydraulic cylinders.    
     
     
         11 . An agricultural tractor loader boom circuit comprising: 
 a source of pressurized hydraulic fluid;    a manually activated control valve in fluid-flow communication with the source of pressurized hydraulic fluid;    a hydraulically controlled loader boom lift circuit, including at least two hydraulic cylinders each with a raise port, a lower port, and a ram therebetween, said raise and lower ports in fluid-flow communication with the control valve;    said control valve having at least one neutral position, one raise position causing pressurized fluid to flow to said raise ports of said hydraulic cylinders to extend said rams, and one lower position causing pressurized fluid to flow to said lower ports of said one hydraulic cylinders to retract said rams; and    a counterbalance relief valve with a relief pressure setting higher than the lift capacity of said hydraulic cylinders, said relief valve positioned between said control valve and said raise ports when said control valve is in said neutral position, thereby providing a positive, zero leak, lock of said hydraulic cylinders.    
     
     
         12 . The boom circuit of  claim 11 , wherein 
 said control valve causing pressurized fluid flow to said lower ports in said hydraulic cylinders when in said lower position;    said relief valve has a relief spring to establish the pressure required to operate said relief valve; and    said control valve, when in said lower position, is piloted internally to said relief valve, causing pressurized fluid to act against said relief spring in a set ratio, to reduce the relief setting, thereby causing said rams to retract.    
     
     
         13 . The boom circuit of  claim 12 , wherein: 
 said hydraulic cylinders are connected to a loader that is raised when said control valve is in said raise position and lowered toward the ground when in said lower position;    said control valve having at least one float position causing said loader to float on the ground;    a reservoir tank on said tractor in fluid-flow communication with said control valve;    said control valve, when in said float position, causes said raise and lower ports to be in fluid-flow communication with said tank, and said control valve is piloted to said relief valve in said set ratio to counterbalance the relief setting of said spring, whereby free fluid flow occurs from said hydraulic cylinders to said tank.    
     
     
         14 . The improvement of  claim 13 , wherein: 
 said set ratio is approximately 10:1.